Secretary of State Rex Tillerson has issued four cables to US diplomatic posts abroad over the past two weeks that recommend additional steps consular officers should take when vetting visa applicants, in the first glimpse of the “extreme vetting” promised by President Trump on the campaign trail.

The cables, published by Reuters on Thursday, revealed specific policies that legal challenges have forced the Trump administration to withdraw, as well as others left in place that expand consular scrutiny.

One such guideline that remains in effect is an order to consular chiefs to establish working groups of law enforcement and intelligence officials to “develop a list of criteria identifying sets of post applicant populations warranting increased scrutiny.” Applicants from those groups, which would apparently vary from country to country, would be subjected to additional screening measures.

It’s unclear exactly how that would depart from screening procedures already in place. But some immigration lawyers and advocates warned it could lead to troubling vetting practices.

"What this language effectively does is give the consular posts permission to step away from the focused factors they have spent years developing and revising, and instead broaden the search to large groups based on gross factors such as nationality and religion," he added.

Another guideline from Mr. Tillerson calls for a “mandatory social media check” for all applicants who have ever set foot in territory controlled by the Islamic State militant group (ISIS). That would constitute a significant expansion of vetting for consular officers, who screen social media only rarely – for instance, in the case of Syrian refugee applicants – due to concerns that it would create an unnecessary swell in backlogs, according to officials consulted by Reuters.

"Theres so much social media out there," said Anne Richard, a former Obama-era assistant secretary of State, told Reuters. "Its not something you can do on a timely basis."

Two of the cables seem to deprioritize the speed of processing, instructing embassies to restrict the number of daily visa interviews even while acknowledging it could cause visa backlogs to rise.

Some security experts have pointed to the interview process as one potential area for improvement in an already extensive process of vetting – a process that has allowed more than 18,000 Syrian refugees to resettle in the US since 2011, none of which have committed or been implicated in plans to carry out a terror attack in the United States, as The Christian Science Monitor’s Howard LaFranchi noted in February.

But that doesn’t mean the system couldn’t be improved further, some say....

For example, the Islamic State took control of official passport offices as it swept across parts of Iraq, Syria, and Libya – and so would have had at its fingertips the means of issuing official-looking documents.

“We know the CIA has worried about that, so part of the heavier vetting may be doubling down on efforts to differentiate between documents generated by ISIS and the real thing,” [James Phillips, a Middle East expert at the Heritage Foundation in Washington] says....

Another improvement would be to have more direct interviewing between US officials and the applicant in the applicant’s language, [David Inserra, a homeland security expert also at Heritage] says.

“That’s not to say the interpreters aren’t doing a good job,” he says, “But you get a better idea of someone’s intentions that can be lost with an interpreter.”

Among instructions rescinded by Mr. Tillerson were those implementing Mr. Trump’s revised executive order banning travel from six countries – an order later blocked by a federal judge in Hawaii in a March 15 injunction.

Visa applicants from Iran, Libya, Somalia, Sudan, Syria, and Yemen, and members of populations identified by consular officers as security risks, would have been required to provide details of where they had lived, traveled, and worked over the past 15 years, as well as all phone numbers, email addresses, and social media handles used in the past five years.